All bone is not the same ! A deer leg bone is seven times denser than a cows !Young animals usually have denser bones than older ones .Secondary projectiles can have a great effect on 'performance '. While I had know about secondary projectiles for years , the first ime I had seen it was when butchering a friends deer. He shot it through th shoulders with a 270. When slicing the ham I found a piece of bone that had come from the shoulder and penetrated half way through the thickest part of the ham !!! Higher velocity also works differently than low velocity. My orthopedic surgeon cousin once described a kid that had been hit with a high velocity 22 , the upper arm shattered into about 100 pieces !!